The integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs, where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs.
Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. For example, three-dimensional fin-like field effect transistor (FinFET) has been introduced to replace a planar transistor. Although existing FinFET devices and methods of fabricating the same have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects. For example, as FinFET technologies have enabled progress towards smaller feature sizes (such as 32 nanometers, 28 nanometers, 20 nanometers, and below), improving properties of source/drain epitaxial features raise challenges in device design and fabrication processes.